1. Field of the Invention
The present invention relates to a position measuring device including a scale carrier member and a scanning device for scanning the scale. The position measuring device may particularly be of the enclosed type.
2. Description of the Related Art
Position measuring devices of the above-described type may be length measuring devices or angle measuring devices which operate in accordance to various physical principles. See, for example, U.S. Pat. Nos. 4,490,915 and 4,731,930.
Position measuring devices of this type are used in machines for determining the relative positions of two or more structural machine components.
If position measuring devices are used in humid surroundings, for example, in so-called processing centers, there is a great danger, even if the position measuring device is of the enclosed type, that moisture vapors penetrate into the interior even due to the smallest leaks. When temperature variations occur, the vapors may condensate and be deposited in an uncontrolled manner, so that temperature variations may negatively influence the operation of the position measuring device.
It is, therefore, the primary object of the present invention to provide a position measuring device which is not susceptible to trouble and ensures high measuring accuracy.